The increasing number of network-connected mobile devices, as well as the increasingly data-intensive applications run on these devices, continue to tax mobile-network infrastructure. As network bandwidth limits are reached, inefficiencies in network architectures and implementations become more apparent. One such inefficiency occurs when a mobile devices moves from a coverage area of a first base-transceiver station to a second; packets sent to or from the first base-transmitter station are dropped and must be re-sent using the second base-transmitter station.
In a prior-art general-packet radio service (“GPRS”) system such as a universal mobile-telecommunication system (“UMTS”), a gateway GPRS service node (“GGSN”) links a packet-switched network, such as the Internet, to the GPRS network. A serving GPRS support node (“SGSN”) is disposed one level of hierarchy below the GGSN and delivers packets to and from radio-network controllers (“RNCs”) in its geographical area. Each RNC controls one or more base-transceiver stations (“NodeB” stations). In such deployments, the mobile network operates as a transport network and is thus unaware of, for example, user-level TCP/UDP/IP sessions and application protocols above TCP/UDP.
FIG. 1 illustrates an example of a network 100 that includes a UMTS radio-access network (“RAN”) and the Internet. A GGSN 102 within the RAN sends and receives content from a server 104 over the Internet 106. The RAN operates only as a transport network, and application sessions are therefore terminated outside the RAN (in, e.g., the Internet 106). When a mobile device 108 moves from a first position 110 to a second position 112, it leaves the coverage area of a first base-transmitter station 114 and enters the coverage area of a second base-transmitter station 116. RNCs 118, 120 use an inter-RNC logical connection 122 in accordance with industry-standard protocols to hand over control-plane and user-plane sessions to the new RNC 120 and new base-transmitter station 116. The hand-over in the user plane happens at the transport level, and any packets lost en route to or from the first base-transmitter station 114 via the first RNC 118 are re-transmitted to the mobile device 108 at its new position 112 using the second RNC 120 and the second base-transmitter station 116 (or other, similar recovery operations are performed).
In other examples, the common point in the network between the first position 110 and the second position 112 may be further “downstream” (e.g., if the two base-transmitter stations 114, 116 are managed by a common RNC 118) or farther “upstream” (e.g., if a first SGSN 120 or GGSN 102 manages the first base-transmitter station 114 and a second, different SGSN or GGSN manages the second base-transmitter station 116). Although packets are dropped in the system 100 during a base-transmitter transfer in each case, the higher upstream the common point, the more packets will be dropped and the greater the inefficiency of the transfer.
Existing Third-Generation Partnership Project (“3GPP”) standards define different types of mobility and relocation operations when a mobile device moves from the coverage area of the first base-transmitter station 114 (e.g., a NodeB/RNC combination in an UMTS network or an eNodeB in a long-term evolution (“LTE”) network) to the second base-transmitter station 116. These operations include intra-NodeB handover, inter-NodeB handover, and inter-RNC handover between two RNCs connected to the same or different SGSNs. The mobility and handover scenarios include soft handover, softer handover, and hard handover. The handover and relocation procedures in the prior-art 3GPP standards operate at the packet-transport level and do not, for example, terminate TCP or UDP sessions.